package com.hmdp.utils;


import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.service.impl.ShopServiceImpl.CACHE_REBUILD_EXECUTOR;
import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {

    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate){
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入Redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <R, ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit){//R的类型是type
        String key = keyPrefix + id;
        //1.从Redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(json)) {//ctrl + q,查看方法具体提示
            //3.存在，直接返回
            return JSONUtil.toBean(json, type);
        }
        //判断命中的是否是空值
        if(json != null){
            //返回一个错误信息
            return null;
        }

        //4.不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        //5.不存在
        if(r == null){
            //将空值写入Redis
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //6.存在，写入Redis
        this.set(key, r, time, unit);
        //7.返回
        return r;
    }

    public <R,ID> R queryWithLogicalExpire(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit){//解决热点key的问题，所以这个业务不可能被穿透的
        String key = keyPrefix + id;
        //1.从Redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(json)) {//ctrl + q,查看方法具体提示
            //3.存在，直接返回
            return null;
        }
        //4.命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
//        Object data = redisData.getData();
        JSONObject data =(JSONObject) redisData.getData();
        R r = JSONUtil.toBean(data, type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            //5.1.未过期，直接返回店铺信息
            return r;
        }
        //5.2 已过期，需要缓存重建
        //6.缓存重建
        //6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2判断是否获取锁成功
        if(isLock){
            //6.3 成功，开启独立线程实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //重建缓存(两个步骤)
                    //1.查询数据库
                    R r1 = dbFallback.apply(id);
                    //2.写入redis
                    this.setWithLogicalExpire(key,r1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }
        //6.4 失败，获取过期的商铺信息
        return r;
    }

    private boolean tryLock(String key){//获取锁
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key){//释放锁
        stringRedisTemplate.delete(key);
    }
}
